_dc.esendex.com has no CNAME records.
Question and response
Question
dig _dc.esendex.com. NS
Answer
The response has no answer records.
Authority
esendex.com. 3370 SOA ns-a.eurodns.com. hostmaster.eurodns.com. 2026022401 43200 7200 1209600 3600
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0